Co-owned co-pending application Ser. No. 326,569, filed Jan. 24, 1973, now U.S. Pat. No. 3,888,008, discloses handpiece wrenches which may be attached to contra-angle handpieces and then manipulated to adjust, or even remove, the chucks of those handpieces. In each of the disclosed forms, the wrench locks the chuck against rotation while at the same time coupling the burtube or rotor to a knurled wheel which is then rotated to turn the burtube and thereby release or tighten the jaws of the chuck. While such construction is highly effective if properly operated, there is a possibility that careless manipulation, or operation by an uninformed or misinformed user, could result in damage to the relatively delicate and precisely fitting parts of the handpiece.
The same is true with regard to the operation of earlier constructions such as the one described in co-owned U.S. Pat. No. 3,325,899. In that construction, the chuck adjustment is performed by a wrench which holds the rotor (burtube) against rotation while permitting rotation of the chuck as one section of the wrench is turned.
With regard to these and other prior art constructions, poor technique in the operation of the wrenches can result in overtightening, jamming, and breakage. In some cases, additional difficulties have been presented because manipulation of the wrenches has resulted in inadvertent partial displacement of the burs, which in turn may cause imbalance, accelerated wear, and unintentional loosening or release of the bur, or because alignment of the mating parts of the wrenches and handpieces has required considerable care to avoid damage to the handpieces. Problems of alignment might appear to have been reduced by those constructions in which the wrenches are provided with sockets that receive portions of the handpieces and serve as guides to locate the wrenches; however, in such constructions there is the further danger that since the shafts and tangs (or lugs) are shrouded from view, misalignment difficulties, although perhaps less frequent, may be more serious. Thus, if such a wrench is canted at the time that the handpiece head is forced into the socket, there is a danger that rotation of the operating wheel of such a wrench will cause the tangs of that wrench to damage that portion of the burtube provided with recesses for receiving such tangs.